Filters that comprise spirally wound filter materials are known in the prior art. For the filtration of air, so-called compact filters are commonly used that are in particular formed of layered filter paper. A corrugated filter paper web is applied onto a flat filter paper web. The thus formed semi-finished product is wound to a filter body or stacked so that a plurality of gas passages that extend parallel to each other are formed. These gas passages are alternatingly closed off by plugs. Incoming air passes axially, parallel to the winding axis, from the raw side (unfiltered fluid side) into the gas passages open at the inlet side and is forced by means of the plugs at the exit side to pass through the filter walls into the neighboring gas passages. From here the filtered air exits through the gas passages open at the exit side to the clean (filtered fluid) side the filter.
WO 2007/035802 A1 discloses a filter and a method for producing such a filter. The filter is produced by winding a web-shaped filter medium. The filter medium is formed of a flat filter medium web and a corrugated filter medium web. Such filters may exhibit a high pressure loss in particular when under great load. Moreover, filters with folds of a filter medium arranged in a star shape are disclosed, for example, in EP 1 191 994 B1. Such filters, however, have a relatively large size and require a lot of mounting space.